University of Nebraska - Lincoln University of Nebraska - Lincoln
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Adam Liska Papers Biological Systems Engineering
2009
Magnitude and Variability in Emissions Savings in the Magnitude and Variability in Emissions Savings in the Corn-Ethanol Life Cycle from Feeding Co-Products to Livestock Ethanol Life Cycle from Feeding Co-Products to Livestock
Virgil R. Bremer
University of Nebraska - Lincoln, vbremer2@unl.edu
Adam Liska
University of Nebraska - Lincoln, aliska2@unl.edu
Terry J. Klopfenstein
University of Nebraska - Lincoln, tklopfenstein1@unl.edu
Galen E. Erickson
University of Nebraska - Lincoln, gerickson4@unl.edu
Haishun Yang
University of Nebraska-Lincoln, hyang2@unl.edu See next page for additional authors
Follow this and additional works at: https://digitalcommons.unl.edu/bseliska Part of the Biological Engineering Commons
Bremer, Virgil R.; Liska, Adam; Klopfenstein, Terry J.; Erickson, Galen E.; Yang, Haishun; Walters, Daniel T.; and Cassman, Kenneth G., "Magnitude and Variability in Emissions Savings in the Corn-Ethanol Life Cycle from Feeding Co-Products to Livestock" (2009). Adam Liska Papers. 5.
https://digitalcommons.unl.edu/bseliska/5
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Authors Authors
Virgil R. Bremer, Adam Liska, Terry J. Klopfenstein, Galen E. Erickson, Haishun Yang, Daniel T. Walters, and Kenneth G. Cassman
This article is available at DigitalCommons@University of Nebraska - Lincoln: https://digitalcommons.unl.edu/ bseliska/5
Magnitude and Variability in Emissions Savings
in the Corn-Ethanol Life Cycle from
Feeding Co-Products to Livestock
Virgil R. Bremer1, Adam J. Liska2*, Terry J. Klopfenstein1, Galen E.
Erickson1, Haishun S. Yang3, Daniel T. Walters3,
and Kenneth G. Cassman3,4
Department of Animal Science1, Department of Biological Systems Engineering2,
Department of Agronomy and Horticulture3, Nebraska Center for Energy Sciences
Research4, University of Nebraska-Lincoln *aliska2@unl.edu, www.bess.unl.edu
year
1998 2000 2002 2004 2006 2008 2010
bil
lion gallons per
y ear 0 2 4 6 8 10
Production of biofuel co-products:
~90% of corn-ethanol biorefineries are currently
natural gas powered dry mills producing
distillers grains for livestock feed
Source: Renewable Fuels Association, Jan. 2009 Total installed capacity (2009):
12.5 billion gallons per year 86% installed since 2001 90% is dry mill
(10% wet mill)
89% is natural gas powered (9% coal, 2.5% biomass)
0 10 20 30 40 50 60 70 80 % o f Co rn Dry M at ter S ta rc h P ro te in L ip id F ib e r L ig n in A s h Mass Energy 0 5 10 15 20 25 30 35 40 % o f DG S Dry M a tt er S ta rc h P ro te in L ip id F ib e r L ig n in A s h Mass Energy Ethanol
Mass and energy content of grain & co-products
Corn grain
17.4 MJ/kg Co-products 22.6 MJ/kg
26% of mass
Feeding co-products to Midwest livestock in 2006
Survey Data for US Corn Belt Livestock CP Feeding, 2006
Livestock Classes: Beef Dairy Swine Total
Corn Belt Production*, million head 11.3 3.2 64.1 78.6
Fraction of US Livestock in Corn Belt*, % 50% 33% 70%
-Fraction of Corn Belt Herd Fed Co-product‡, % 63% 49% 40%
-Current DGS Feeding Practices in the Midwest 2006 (Roughly 33% of all US co-product produced)
Dietary DGS inclusion Level**, % of dietary intake 20% 10% 9%
-Total DGS use‡, million Mg (% inclusion x animals fed) 2.4 1.3 0.6 4.3
Distribution of DGS use‡, % of total 56% 30% 14% 100%
Ethanol Industry to Supply DGS‡, Billion L/year 3.4 1.9 0.9 6.2
*NASS (National Agricultural Statistics Service). 2007. Ethanol co-products used for livestock
• Co-product GHG credits can represent 10 to 40% of
total life cycle GHG emissions (Liska et al. 2009)
• Abundant CP has led to new feeding practices
• Research presented here: Updated CP credit for
the BESS model for the corn-ethanol life cycle from beef cattle only to recent co-product feeding
practices for beef, swine, and dairy livestock
• Performed meta-analysis and data summary for
current beef, swine, and dairy feeding parameters: 1) dietary inclusion level for CP feeding (% diet)
2) efficiency of feeding different co-product types to different livestock (e.g. gain-to-feed ratios)
3) Displacement ratios of conventional feeds
(utilized new survey data for biorefinery efficiency)
Analysis of co-product (CP) GHG emissions
credits for the life cycle of corn-ethanol
Region: - - - Midwest Iowa Nebraska Texas
Co-product type produced & fed
Dry distillers grains (dm), % 100
-100 0.57 0.43 Urea 0.0 0.0 0.064 0.036 0.012 0.055 0.064 1.00 35 72 14 0
Modified distillers grains (dm), %
100 100 -100 -0.45 32.5 14 19 0
Wet distillers grains (dm). %
0.55 -100 -1.21 0.0 32.5 14 67 100 Beef cattle, % 56 18 74 97 Dairy cattle, % 30 10 2 3 Swine, % 14 72 24 0
Dietary substitutions, kg kg-1 co-product (dry matter)
Corn 0.91 0.68 1.20 1.35
Soybean meal 0.23 0.36 0.07 0.02
1.00 1.27
Total 1.17 1.06 1.33 1.43
Source: Bremer et al. Journal of Environmental Quality, in press
Co-product types, livestock classes, and resulting dietary substitutions from updated BESS model
327 316 301 426 230 261 235 250 290 236 347 274 287 311 360 382 365 275 226 48% 54% 53% 51% 51% 48% 48% 45% 44% 52% 47% 49% 47% 51% 56% 42% 45% 43% 40%
kg CO2e per Mg Grain
411- 423 319 - 341 342 - 364 365 - 387 388 - 410 226 - 249 250 - 272 273 - 295 296 - 318
Source: Liska et al, Journal of Industrial Ecology, 13, 58-74 (2009)
Regional variability in corn production GHG-intensity
is also relevant for corn substitutions in the CP credit
(e.g. larger credit in Texas)
Southern US has lower crop yields and higher fertilizer rates than the Corn Belt
Regions Midwest Iowa Nebraska Texas
Net ethanol Intensity, gCO2e MJ-1 52.3 51.6 43.7 50.0
GHG emissions credit, gCO2e MJ-1
Corn (regional sources) 9.64 6.50 12.8 22.1
Soybean meal 2.82 4.56 0.91 0.21
Urea 1.60 0.52 2.43 2.85
Diesel fuel -0.10 -0.04 -0.21 -0.26
Enteric fermentation 1.27 0.424 2.52 3.42
Total 15.2 12.0 18.4 28.3
Biorefinery thermal energy* MJ L-1 7.72 7.60 5.70 4.91
GHG Reduction relative to gasoline, % 46.5% 47.2% 55.3% 48.8%
Source: Bremer et al. Journal of Environmental Quality, in press
Components of BESS model GHG emissions credit and life cycle impacts based on above dietary substitutions
*A equation was developed between co-product types produced (% wet,
-40 -20 0 20 40 60 80 100 30.8 26.0 34.4 53.1 23.8 31.4 31.7 36.6 Biorefinery emissions
Cropping system emissions
%
Co-product emissions credit
% % Corn-Ethanol Systems GHG Emissions, gCO2e MJ-1 -15.2 -18.4 -28.3 -12.0 % % Texas Midwest Iowa Nebraska
GHG emissions credits and life cycle impacts
Variability in co-product GHG emissions credits for individual biorefineries/regions depending on
type of CP produced and livestock class fed DDGS
WDGS
dairy &
swine Source: Bremer et al. Journal of Environmental Qualitybeef , in press
Results of BESS model simulations
Gasoline:
97.7 gCO2e/MJ
Life cycle GHG emissions intensity and % reductions for corn-ethanol compared to gasoline, depending on
co-product variability & energy savings for drying CP DDGS
WDGS
dairy & swine
beef
Source: Bremer et al. Journal of Environmental Quality, in press Results of
BESS model simulations
Recommendations: Data needed for
improvements and reduction in uncertainty
1) Types and characteristics of co-products produced at corn-ethanol biorefineries in the U.S.
2) Types of livestock being fed co-products in the entire U.S.
3) Inclusion level of co-products in livestock diets
4) Hauling distances between co-product production and use
5) Amount of co-product exported
6) Differential N2O emissions during co-product feeding
need to be better understood (IPCC does not capture regional variability)
7) Emission factors in the life cycle of biofuels need to be standardized to determine a consensus co-product credit value (more intense upstream emissions will increase co-product value)
Conclusions
• Co-product GHG emissions credit varied by >2-fold,
from 11.5 to 28.3 gCO2e per MJ of ethanol produced
• Co-product GHG emissions credit depend on
-types of co-products produced
-proportion fed to beef cattle vs. diary or swine
-location of corn production; the CP credit is highest
in regions where GHG kg-1 grain are highest
• Depending on CP production types and feeding
livestock classes, corn-ethanol net life cycle GHG
intensity is 44-56 gCO2e per MJ
• Midwest corn-ethanol reduces GHG emissions
compared to gasoline by 47% on average, with co-products offsetting 23% of positive emissions
Funding support
• USDA NC506 Regional Research • Western Governor’s Association • US Department of Energy
• University of Nebraska Center for Energy Sciences Research
• Environmental Defense
References
• Bremer V.R., A.J. Liska, T.J. Klopfenstein, G.E. Erickson, H.S. Yang, D.T. Walters, K.G. Cassman, Emissions Savings in the Corn-Ethanol Life Cycle from
Feeding Co-Products to Livestock, Journal of Environmental Quality, in press
• Liska A.J., H.S. Yang, V.R. Bremer, T.J. Klopfenstein, D.T. Walters, G.E. Erickson, K.G. Cassman, Improvements in Life Cycle Energy Efficiency and
Greenhouse Gas Emissions of Corn-Ethanol, Journal of Industrial Ecology,
13, 58-74 (2009)
• Liska A. J., and K.G. Cassman, Response to Plevin: Implications for Life
Cycle Emissions Regulations, Journal of Industrial Ecology, 13:508-513
(2009)
• Klopfenstein, T., G. Erickson, V. Bremer. Use of Distillers Byproducts in the
Beef Cattle Feeding Industry. Journal of Animal Science, 86, 1223-1231
(2008)
• Liska A.J. , and R.K. Perrin, Indirect Land Use Emissions in the Life Cycle of
Biofuels: Regulations vs. Science, Biofuels, Bioproducts, & Biorefining, 3,
318-328 (2009)
• Liska A. J., and K.G. Cassman, Towards Standardization of Life-Cycle
Metrics for Biofuels: Greenhouse Gas Emissions Mitigation and Net
Energy Yield, Journal of Biobased Materials and Bioenergy 2, 187-203 (2008)
• Perrin R.K., Fretes N., Sesmero J.P. Efficiency in Midwest US Corn Ethanol
